This invention relates to a fuel oil supply system, and more particularly to a method and apparatus for minimizing the transfer of impurities in fuel oil from a storage vessel to the site of use of said oil.
In the utilization of liquid fuels to generate heat or energize engines, filter means are generally employed to remove suspended impurities from the fuel in order to protect the equipment which utilizes said fuel. Suspended impurities can be of a solid, semi-solid or liquid nature. Although such impurities may occur by virtue of inadvertent contamination in the course of processing and transporting the fuel, most liquid hydrocarbon fuels deposit gel-like impurities merely on aging.
A commonly used system for the heating of buildings such as residential homes and industrial buildings involves the burning of a hydrocarbon fuel known as number 2 grade heating oil in a plenum chamber which heats air or water for circulation to its point of intended use. As distinguished from the more volatile kerosine, which can be ignited in an open pool, number 2 grade heating oil must be atomized or vaporized to facilitate burning. Atomization of the oil is generally achieved by means of a burner comprising a spray nozzle fed by a pump which pressurizes the oil to about 100 pounds per square inch, or higher. The storage vessel for the heating oil generally consists of an underground reservoir tank located outside the building.
The pump which pressurizes the oil for atomization also serves to withdraw the oil from the storage tank through a pipline known as a suction line. Because the pump is designed to be self-purging and self-priming, it withdraws more oil from the storage reservoir than it actually pressurizes for burning. The excess oil is returned to the reservoir via a separate pipeline known as the return line. In the operation of a typical oil burner unit for heating a private residential dwelling, oil is taken from the storage tank at a rate of about 16 to 20 gallons per hour, the delivery through the nozzle may range from about 0.75 to 3.0 gallons per hour, and the remaining oil is returned to the storage tank.
A filter is positioned within the suction line between the pump and the storage tank to protect the pump and nozzle from impurities suspended in the oil. Separate supplemental filters or strainers may additionally protect the pump and nozzle.
In the course of prolonged storage, the fuel oil forms gel particles, most of which settle to the bottom of the reservoir tank to form a sludge-like deposit. When a new supply of oil is added to the storage tank, its turbulent effect stirs up the sludge sediment, causing considerable amounts of sludge to be drawn into the filter. When the filter becomes clogged with sludge, the system will either function improperly, or will cease functioning. Restoration of a malfunctioning fuel oil system may require cleaning or replacement of the filter, nozzle, pump and/or supply lines.
It is an object of the present invention to prolong the operating effectiveness of a filter in the suction line of a fuel oil transfer system. It is another object to prolong the operating effectiveness of a fuel oil filter preceding a burner by minimizing the amount of oil passed through said filter while maintaining satisfactory operation of said burner. Other objects and advantages will become apparent hereinafter.
The use of supplementary fuel storage reservoirs or tanks interposed between an underground storage tank and equipment for the use or transit of the fuel have been earlier disclosed. Such supplementary reservoirs, as the tank and associated float valve disclosed in U.S. Pat. No. 1,595,503, have generally served as overflow tanks in metering systems. The use of a supplementary tank in a manner so as to secure improvements in filter effectiveness has not heretofore been disclosed or suggested.